Congrats! A December wedding is totally possible! My best advice, research, research, research! Everything depends on your budget and what you are willing to spend. Once you decide on which resort etc I would book it soon, you'd be surprised at fast time slots for weddings book up- even this far in advance. I sent our Save the Dates via email because we had time sensitive information regarding a group booking discount. I sent out our invites about 9 months out to give people as much time as possible. I recommend having an earlier RSVP date so you can get a better idea of numbers, this is the one thing I would have changed because I am bringing all of our decorations with us and has been hard to estimate how much stuff I will need. As for a photographer, this was one of my highest priorities, at the end of the day all you have left are pictures. I was willing to spend a bit more on a photographer, we are bringing one with us but there are a ton of local photographers where ever you decide to go. As of now, we do not have any off site guests and I hope it will stay this way, all resorts charge a fee for a day pass for these guests to attend the wedding- this cost can quickly add up if you have a lot of guests who chose not to stay at the same resort. Hope this helps! Good luck and have fun planning!